电力需求与定价(10)

mutually self-consistent. In practice, uncertainties in

price elasticities of demand and other data may dictate a more

pragmatic approach in which the LRMC results would be used

after only one iteration to devise new power tariffs and to implement

them. The demand behavior is then observed over

some time period; the LRMC is re-estimated and tariffs are

revised to move closer to the optimum, which may itself have

336 PROCEEDINGS OF THE IEEE, VOL. 69, NO. 3, MARCH 1981

shifted, as described previously. An extreme form of price

feedback could result in a shift of the peak outside the original

peak period, especially if the latter was too narrowly defined.

That is, peak load pricing may shift the demand peak, from

one pricing period to another. If sufficient data on the price

elasticity of demand were available, theory indicates that each

potential or secondary peak should be priced to keep its magnitude

just below the available capacity level. Since the necessary

information would rarely be available in practice, a combination

of techniques including use of a sufficiently wide peak

period, redefining the peak period to include both the actual

and potential peaks, direct switching of certain consumer

loads, and so on, may be used to avoid the shifting peak

problem.

Second, the interrelated issues of supply and demand uncertainty,

reserve margins, and costs of shortages raise certain

problems. Since the least cost system expansion plan to meet

the demand forecast is generally determined assuming some

(arbitrary) target level of system reliability (e.g., loss-of-load

probability (LOLP), reserve margin, etc.), the marginal costs

depend on the target reliability level [ 261. However, economic

theory suggests that reliability should also be treated as

a variable to be optimized, and both price and capacity (or

equivalently, reliability) levels should be optimized simultaneously.

The optimal price is the marginal cost price, while

the optimal reliability level is achieved when the marginal cost

of capacity additions are equal to the expected value of economic

cost savings to consumers due to electricity supply

shortages averted by those capacity increments. These considerations

lead to a more generalized approach to system expansion

planning [ 25 ] .

Consider a simple expression for the net benefits NB of electricity

consumption, which is to be maximized:

NB(D, R=) TB(D)- SC(D, R ) - OC(D, R )

where TB is total benefits of consumption if there were no

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